Go against the law of personal boundaries...and make sure you eat sumn that will kill your breath like onions. and start talking in their faces.
Fart..in an elevator..and claim that you did it. and just keep doing it.
Pick your noes...pretend to eat it or flick it. when in close areas or near ppl

i got someone annoying when i was in school (computer programming) the guy ask the same question so many time when teacher explain to him if he understand than he say yes than again few minute later asking the same question.... also when you ask him search for the answer in google he look up his screen open google 10 sec than ask again i cant find the answer ... didnt take his time to search.... sooooo annoying